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It may even exist, but this has not yet been fully proven by experts. “All mammals and birds ever studied sleep. However, it is not possible to say that there are no animals that never sleep because the overwhelming majority of species have never been studied”, says neurophysiologist César Timo-Iaria, from the University of São Paulo (USP). Biologists believe, however, that some animals can remain continuously awake, such as sharks. “They have never been caught sleeping, but it has not yet been experimentally possible to prove whether, in fact, they never sleep”, says biologist Otto Bismarck Gadig, from the São Paulo State University (Unesp), an expert on these marine beasts.
For now, it is known that sharks are able to lower their metabolism in stressful situations or when they are resting in underwater caves. A similar phenomenon occurs with whales. “At first, cetaceans don’t sleep, but they suffer a low metabolism that leads to a stage similar to sleep”, says biologist Mário Rolo, also from Unesp.